Fatty acid mono‐ and diesters of diglycerol constitute the major portion of commercial polyglycerol esters; hence, their composition influences the performance of the latter as emulsifiers. The correlation of structure of the fatty acids in the mono‐ and diesters with surfactant properties is of interest. Linear diglycerol was isolated from polymerized glycerol by acetonation, fractional distillation and regeneration. Diglycerol mono‐ and diesters of undecenoic, lauric, stearic, oleic and ricinoleic acids were prepared by reacting diglycerol and fatty acids in a refluxing mixture of acetonitrile‐tetrahydrofuran (75:25) in the presence of p‐toluenesulfonic acid and molecular sieves. Mono‐ and diesters were separated by silica gel column chromatography, and their purities were ascertained by thin layer chromatography and determination of saponification value. The structures were confirmed by periodic acid oxidation, chemical‐ionization mass spectrometry and 13 C‐NMR spectroscopy. Surfactant properties of the esters were determined. Monoesters showed higher ability in surface tension reduction, emulsification and foaming than the diesters. Short‐chain fatty acid esters showed better surfactant properties than the long‐chain fatty acid esters. The presence of a central double bond in the lipophilic part of the monoesters reduced emulsion stability. The presence of a hydroxy group in acyl chain retarded foaming and surface tension reducing power.

The effects of variations in pressure (20-40 kg/em2), oil-to-water ratio (1:0.4-1:1, w/w) and time (0-8 hr) on the extent of hydrolysis of castor oil were studied. Higher pressure , lower oil-to-water ratio and longer duration gave higher percentage splits. At 40 kg/em ~ pressure and an oil-to-water ratio of 1:1, ca. 92% split was obtained in 8 hr. When the oil was hydrolyzed in 2 stages at 20 kg/cm ~ with an oil-to-water ratio of 1:0.4, ca. 96% split was obtained in a total period of 10 hr. Splitting at 20 kg/cm 2 gave minimal amounts of dienoic acids because of the decomposition of estolides.